What is Powder Metallurgy Process | Advantages and Disadvantages Of Powder Metallurgy
Introduction Of Powder Metallurgy
The technique of powder metallurgy combines unique technical features with cost effectiveness and generally used to produce sintered hard metals known as ‘carbides’ or ‘tungsten carbides’.
This technique deals with the production of metal and non metal powders and manufacture of components.
Powder metallurgy is generally used for iron based components.
The powders used as raw material can be elemental, pre-alloyed, or partially alloyed.
Elemental powders like iron and copper are more compressible and produce pressed compacts with good strength.
Pre-alloyed powders are harder but less compressible therefore require higher pressing loads to produce high density compacts.
Powder metallurgy technique has many advantage as well as limitation.
Two main techniques used to form and consolidate the powder are sintering and metal injection molding. Recent developments have made it possible to use rapid manufacturing techniques which use the metal powder for the products. Because with this technique the powder is melted and not sintered, better mechanical strength can be accomplished.
Advantages Of Powder Metallurgy:
- Parts can be produced from high melting point refractory metals with respectively less difficulty and at less cost.
- Production rates are high even for complex parts. This is primarily because of the use of automated equipment in the process.
- Near net shape components are produced. The dimensional tolerances on components are mostly such that no further machining is needed. Scrap is almost negligible.
- Parts can be made from a great variety of compositions. It is therefore much easy to have parts of desired mechanical and physical properties like density, hardness toughness, stiffness, damping, and specific electrical or magnetic properties.
- Parts can be produced with impregnation and infiltration of other materials to obtain special characteristics needed for specific applications.
- Skilled machinists are not needed, so labour cost is low
- Parts with controlled porosity can be produced
- Bi-metallic products, sintered carbides and porous bearings can be produced only by this process.
Limitations Of Powder Metallurgy :
- High cost of metal powders compared to the cost of raw material used for casting or forging a component. A few powders are even difficult to store without some deterioration.
- High cost of tooling and equipment. This is particularly a limitation when production volumes are small.
- Large or complex shaped parts are difficult to produce by PM process.
- Parts have lower ductility and strength than those produced by forging.
- Uniformly high – density products are difficult to produce.
- Some powders (such as aluminum, magnesium, titanium and zirconium) in a finally divided state present fire hazard and risk of explosion.
- Low melting point metal powders (such as of zinc, tin, cadmium) give thermal difficulties during sintering operation, as most oxides of these metals cannot be reduced at temperatures below the melting point.
Applications of Powder Metallurgy
Cutting Tools and Dies.
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